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On 6 Sep 2002, at 12:50, Brian wrote: > vaccum advance can come in at either place jim. my first set of baby > dells came with the vac port on the manifold and it operated the vac > just fine. The manifold vacuum goes down with increasing throttle and decreasing rpm while most VW distributors that I'm aware of give increasing advance with increasing vacuum. If you just hooked up one of these distributors to manifold vacuum you would get max advance at idle, min adv at low speed WOT, increasing with rpm, and decreasing with throttle. While portions of this don't sound too bad it doesn't sound too good overall. Did you have a different kind of vacuum arrangement on the dist you had? Taking the vacuum from the venturi gives a vacuum which is proportional to air flow: min at idle and increasing with both rpm and throttle opening. This is a pretty good match to what the engine needs. The Bill Fisher book points out that the replacement mech adv dists became popular BECAUSE the aftermarket carbs didn't come with a vacuum advance ports. I'd have thought that if using manifold vacuum were a reasonable option it would have been used, and mentioned in that book. OTOH, I agree that its omission proves nothing. - Jim Adney jadney@vwtype3.org Madison, WI 53711-3054 USA ------------------------------------------------ To unsubscribe, E-mail to: <type3-off@vwtype3.org> For more help, see http://vwtype3.org/list/